1. Field of the Invention
This invention relates broadly to optical machine-readable data codes. More particularly, this invention relates to methods and apparatus for generating and printing (or displaying) optical machine-readable data codes as well as methods and apparatus for reading and decoding optical machine-readable data codes.
2. State of the Art
There are many different types of optical machine-readable data codes in use today. The constructs and underlying meaning for a set of data codes is defined by a symbology. The specification of a symbology includes the encoding of the single digits/characters of a message (also commonly referred to as a codeword) as well as constructs for identifying the boundary of the encoded data. For example, modern bar code symbologies typically include a quiet zone as well as unique start and stop markers to aid in identifying the boundary of the encoded data. The bar code symbologies can also employ a check digit for error detection as is well known.
There are a wide variety of data code symbologies in use today, including linear bar codes that are typically be read by a laser scanner as well as two dimensional data codes that are typically read by a digital camera sensor such as a charge coupled device (CCD). Most data code symbologies are designed to be printed on a label or some other object. Some data code symbologies are designed to be displayed ephemerally, e.g. on a television screen.
Typically, data code symbologies are read by a machine with the help of a human. The human locates the data code and orients the data code and/or the machine so that the machine can read the data code.